Dance does madness well - it can suggest a range of love-crazed, grief-stricken and supernaturally spooked frenzies. But Fleur Darkin's Augustine is an unusually considered piece on the topic.

Its title refers to a 15-year-old girl who was confined to an asylum in late 19th-century Paris, suffering from the symptoms of extreme hysteria. Despite experiencing nightmares, narcolepsy and an inability to speak, Augustine seems to have enjoyed parading her physical symptoms for the eminent Dr Charcot and his interested public. A hundred years later, when Darkin saw documentary photographs of Augustine's twitching, traumatised movements, she concluded that, in some determined way, the troubled teenager was trying to dance.

Darkin's piece is not the story of Augustine herself, but a meditation on the physical and the emotional possibilities contained within her damaged body language. Initially, Darkin's cast of six men and women are restricted to an almost cliched vocabulary of the insane - frozen foetal crouches, thrashing limbs and grinning bunny hops. Yet, as the language is unpacked into longer choreographed vignettes, slivers of sweetness, humour and fantasy emerge, along with a liberating energy.

Throughout the piece, Darkin also has her dancers slip almost randomly between the roles of patient and doctor. The point here is not simply to make the obvious point that madness and sanity are divided by the thinnest of psychological lines. Darkin is also exploring the attachment that forms between inmates and carers as even the harshest of asylum practices - enforced sponge baths, invasive diagnosis, physical restraint - evolve into duets of unexpectedly delicate, funny sympathy.

The dancers perform this material with intelligence and conviction, even though they have disappointingly less to play with towards the end of its 50 minutes. Still, the production is given constant dynamic shape by Sarah Moody's excellent score. Performed live by her and the dancers, its deceptively simple layering of violin, cello and voice creates a haunting soundworld that is part nursery, part nightmare - but always tenderly humane.

· At Old Town Hall, Hemel Hempstead (01442 228091), on May 9. Then touring.